A cognitive radio technology is a most promising technology that solves a current problem of frequency spectrum resource scarcity. Unoccupied available frequency bands may be found mainly by perceiving a wireless frequency spectrum environment, and these frequency bands are dynamically accessed on the premise of not disturbing master subscribers.
To implement identification of a current radio environment, each regulation organization, such as Federal Communications Commission in America, Confederation of European Posts and Telecommunications, or Office of Communications in Britain, sets up a database. For the digital television field, the database stores use information of all television frequency spectrums, including a location of a television tower, a used frequency band, a coverage range, and so on, and a cognitive device may acquire a frequency spectrum condition of a current location by querying the database, thereby using a frequency spectrum that is not used by the digital television.
At present, each regulation organization hopes to push the standardization of the cognitive radio technology for television white frequency spectrums. Therefore, a cognitive device can use a white frequency spectrum resource to implement normal communication only after registering in the database, where the cognitive device may be a terminal. In a conventional registration process, a terminal can determine that registration is successful only after receiving a registration response message sent by the database. If the database does not return a registration response message for a long time, the terminal retains a connection to a network but cannot perform normal communication, which occupies a large number of network resources.